Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Formal mapping

Let us briefly mention some formal aspects of the above-introduced formalism, which have been discussed in detail by Blaizot and Marshalek [218]. First, it is noted that the both the Schwinger and the Holstein-Primakoff representations are not unitary transformations in the usual sense. Nevertheless, a transformation may be defined in terms of a formal mapping operator acting in the fermionic-bosonic product Hilbert space. Furthermore, the interrelation of the Schwinger representation and the Holstein-Primakoff representation has been investigated in the context of quantization of time-dependent self-consistent fields. It has been shown that the representations are related to each other by a nonunitary transformation. This lack of unitarity is a consequence of the nonexistence of a unitary polar decomposition of the creation and annihilation operators a and at [221] and the resulting difficulties in the definition of a proper phase operator in quantum optics [222]. [Pg.304]

In chemical reactions and conformational changes, such as the process modeled by the formal reaction path p, the matrix 1D(X ) as well as the vector a K) change as the nuclear configuration K varies. Consider the path p as a formal mapping from the unit interval / to the metric nuclear configuration space M [13],... [Pg.75]

Draw the Lewis structure of each carbocation (show all formal charges). Do these structures provide any indication of which carbocation will form most readily Explain. Examine the electrostatic potential map of each carbocation. Which carbocation shows the greatest localization of positive charge Which shows the greatest delocalization of charge Where does the positive charge go in the most delocalized ion Do these observations provide any indication of which caibocation will form most readily ... [Pg.91]

Compare and contrast the electrostatic potential map of a typical detergent with that of a typical soap (stearate). Which part of each molecule will be most water soluble (hydrophilic) Draw a Lewis structure that describes each molecule s water-soluble group (make sure you indicate all necessary formal charges and lone pairs). Which part(s) of each molecule will be most grease soluble (lipophilic) What kinds of atoms and bonds are found in these groups ... [Pg.157]

It should be realized that unlike the study of equilibrium thermodynamics for which a model is often mapped onto Ising system, elementary mechanism of atomic motion plays a deterministic role in the kinetic study. In an actual alloy system, diffusion of an atomic species is mainly driven by vacancy mechanism. The incorporation of the vacancy mechanism into PPM formalism, however, is not readily achieved, since the abundant freedom of microscopic path of atomic movement demands intractable number of variational parameters. The present study is, therefore, limited to a simple spin kinetics, known as Glauber dynamics [14] for which flipping events at fixed lattice points drive the phase transition. Hence, the present study for a spin system is regarded as a precursor to an alloy kinetics. The limitation of the model is critically examined and pointed out in the subsequent sections. [Pg.84]

Strange Attractors The motion on strange attractors exhibits many of the properties normally associated with completely random or chaotic behavior, despite being well-defined at all times and fully deterministic. More formally, a strange attractor S is an attractor (meaning that it satisfies properties (i)-(iii) above) that also displays sensitivity to initial conditions. In the case of a one-dimensional map, Xn+i = for example, this means that there exists a <5 > 0 such that for... [Pg.171]

Dimethyl sulfoxide, electrostatic potential map of, 40 formal charges in, 40-41 Sn2 reaction and, 371... [Pg.1294]

Food, catabolism of, 1126-1128 Formal charge, 40-41 calculation of, 41-42 summary table of, 42 Formaldehyde, dipole moment of, 39 electrostatic potential map of. 167, 704... [Pg.1298]

Contextual design is a flexible software design approach that collects multiple customer-centered techniques into an integrated design process [7]. The approach is centered around contextual inquiry sessions in which detailed information is gathered about the way individual people work and use systems and the associated information flow. The data from each contextual inquiry session are used to create sequence models that map the exact workflow in a session along with any information breakdowns, flow models that detail the flow of information between parties and systems (much akin to but less formal... [Pg.234]

These pharmacophore techniques are different in format from the traditional pharmacophore definitions. They can not be easily visualized and mapped to the molecular structures rather, they are encoded as keys or topological/topographical descriptors. Nonetheless, they capture the same idea as the classic pharmacophore concept. Furthermore, this formalism is quite useful in building quantitative predictive models that can be used to classify and predict biological activities. [Pg.311]

A formal induction of mappings from measured operating data to process conditions is composed of the following three tasks (Fig. 3) ... [Pg.213]

Conventional implementations of MaxEnt method for charge density studies do not allow easy access to deformation maps a possible approach involves running a MaxEnt calculation on a set of data computed from a superposition of spherical atoms, and subtracting this map from qME [44], Recourse to a two-channel formalism, that redistributes positive- and negative-density scatterers, fitting a set of difference Fourier coefficients, has also been made [18], but there is no consensus on what the definition of entropy should be in a two-channel situation [18, 36,41] moreover, the shapes and number of positive and negative scatterers may need to differ in a way which is difficult to specify. [Pg.18]

The next update of the null hypothesis would incorporate a zero-order description of bonding, in terms of a prior prejudice of standard chemical groups. The MaxEnt map then will tell us about the subtle differences induced in formally equivalent chemical bonds by conjugation, stacking, and other intra- and intermolecular interactions. To achieve this degree of accuracy, the refinement of structural parameters... [Pg.34]

All comments on Nyquist plots are made without the need of formal hand sketching techniques. Strictly speaking, the polar plot is a mapping of the imaginary axis from co = 0+ to You ll see... [Pg.148]

At a certain stage in the refinement, the electron density map is interpreted using a model representation of the charge density distribution to extract the atomic coordinates. A commonly used scattering formalism is the independent-atom model (IAM), in which the total charge density in the crystal is approximated by the superposition... [Pg.353]

Figure 3.1 Electrostatic potential maps for BF3, NH3, and the product that results from reaction between them. Attraction between the strongly positive region of BF3 and the negative region of NH3 causes them to react. The electrostatic potential map for the product for the product shows that the fluorine atoms draw in the electron density of the formal negative charge, and the nitrogen atom, with its hydrogens, carries the formal positive charge. Figure 3.1 Electrostatic potential maps for BF3, NH3, and the product that results from reaction between them. Attraction between the strongly positive region of BF3 and the negative region of NH3 causes them to react. The electrostatic potential map for the product for the product shows that the fluorine atoms draw in the electron density of the formal negative charge, and the nitrogen atom, with its hydrogens, carries the formal positive charge.

See other pages where Formal mapping is mentioned: [Pg.109]    [Pg.443]    [Pg.443]    [Pg.621]    [Pg.97]    [Pg.621]    [Pg.365]    [Pg.611]    [Pg.297]    [Pg.16]    [Pg.68]    [Pg.109]    [Pg.443]    [Pg.443]    [Pg.621]    [Pg.97]    [Pg.621]    [Pg.365]    [Pg.611]    [Pg.297]    [Pg.16]    [Pg.68]    [Pg.509]    [Pg.529]    [Pg.156]    [Pg.205]    [Pg.47]    [Pg.204]    [Pg.251]    [Pg.319]    [Pg.369]    [Pg.40]    [Pg.221]    [Pg.206]    [Pg.178]    [Pg.4]    [Pg.57]    [Pg.109]    [Pg.208]    [Pg.192]    [Pg.39]    [Pg.69]    [Pg.136]   
See also in sourсe #XX -- [ Pg.297 ]




SEARCH



© 2024 chempedia.info